1. Field of Invention
This application relates to elastomeric reactor blend compositions and to continuous processes for making an elastomer composition that comprises a first polymer and a second polymer with differing levels and/or types of crystallinity.
2. Description of Related Art
Embodiments of the invention relate to elastomeric reactor blend compositions. There have existed ongoing efforts to make polymer compositions having a desirable balance of properties and attributes, leading to enhanced compositions that are useful in a number of applications. Such composition enhancements can manifest themselves in a variety of ways depending on the specific application and the specific blend contemplated. Such enhancements include, but are not limited to, (1) processibility in the molten state in such processes as milling, extrusion, calendering and injection molding; (2) initial physical properties in a solid state such as toughness, tack, adhesion, tear resistance, tensile and elongation (3) improvements in cure rate and state if curing or vulcanization are intended; and (4) long-term physical properties such as heat aging as defined by the retention of such physical properties at elevated temperatures. A variety of approaches have been suggested to obtain polymer compositions with the desired properties and attributes, but those approaches have experienced various shortcomings.
U.S. Pat. No. 6,635,715 discloses blends of an ethylene propylene elastomer having a low level of isotactic crystallinity with different amounts of a highly crystalline propylene based polymer. The blends are produced by physically blending the components.
U.S. Pat. No. 6,329,477 discloses the use of series reactors in the production of polymer compositions using a biscyclopentadienyl type metallocene catalyst but the compositions do not have two polymers with widely varying propylene contents. Other patents relating to the production of polymer compositions are U.S. Pat. Nos. 6,319,998 and 6,207,756.
WO 98/02471 and U.S. Pat. No. 6,545,088 disclose the use of series reactors in the production of EP rubbers using a monocyclopentadienyl type metallocene catalyst.
WO 03/040201 discloses the use of series reactor operations using a non-metallocene type catalyst to produce polymer compositions with varying crystallinity. No indication is provided for using implementation in continuous operation using a recycle or process conditions permitting molecular weights etc. appropriate for commercial elastomer use.
Other background references include U.S. Pat. No. 6,747,114, U.S. Patent Application Publication 2004/198913, WO 1997/36942, and WO 2002/34795.
It is among the objects of the invention to scope new polymer compositions where the benefits of series and/or parallel reactor operation are exploited to provide useful elastomers having an overall Mooney from 16 to 180, and to employ the series reactor recycle yet at the same time provide polymers in the composition with have different crystallinity (isotactic propylene type, ethylene type, or fully amorphous). It also among the objects of the invention to provide continuous multiple reactor process conditions that enable such polymer compositions to be made efficiently on commercial scale plants.